This invention relates to MOSgated power semiconductor device and more specifically relates to a temperature sensing structure for such devices which occupy a reduced die area, and which are less sensitive to noise due to the power circuit operation.
The use of diodes or bipolar transistors for the temperature sensing of a power MOSFET die is shown for example, in U.S. Pat. Nos. 4,760,434; 4,896,199; 4,903,106; 5,100,829; 5,289,028; 5,389,813; 5,536,958; and 5,545,914.
Such devices are also employed in commercially available devices, such as the WAVEFET.TM. series of the Motorola Corporation which includes a device type MTC3400.
The prior art devices are arranged in such a way that the temperature sensing diode terminals are inherently capacitively coupled to noisy power terminal, for example, the center terminal of power MOSFETs connected in a "totem-pole" arrangement. Therefore, the temperature sensing device output has noise superimposed thereon to reduce its usefulness and accuracy. Further, the temperature sensing structure has taken a relatively large percentage of the active area of a chip or die.
It would be very desirable to provide a temperature sensing structure which occupies a smaller portion of the available active area of a die of given size, and it would be very desirable to isolate the noise coupled back to the sensor to make its operation more reliable and accurate.